Obesity is considered one of the nation's most important public health problems because of the evidence linking it with premature mortality and certain types of morbidity including diabetes mellitus, hypertension, and cardiovascular disease. Despite the attention given to studying the effect of obesity on morbidity and mortality, relatively little research has examined other dimensions of health-related quality of life. The proposed research is designed to address this gap in the literature by applying cumulative disadvantage theory to better understand how excess body weight may affect physical disability and self-assessed health across the life course. According to cumulative disadvantage theory, the overarching research question is: Do the health disadvantages of obesity, assessed by body mass index (BMI), increase of decrease with age? Toward this end, we propose two main hypotheses and several supplementary hypotheses to be tested: Hypothesis 1. The effect of BMI on functional disability increases with age. (This hypothesis anticipates that high BMI will produce more heterogeneity and health inequality over the life course). Hypothesis 2. The negative effect of BMI on health assessments increases with age. (More generally, this hypothesis anticipates that a high BMI lowers health ratings and leads to a pernicious cycle of health decline over the life course). The research tests these hypotheses with two nationally representative panel studies. (1)The National Health and Nutrition Examination Survey I: Epidemiologic Follow-up Study (NHEFS) is a four-wave, 20-year panel study of adult Americans (N=6,931 at baseline). (2)Americans' Changing Lives (ACL) is two-wave, 3-year panel study of adult Americans (N=3,617 at baseline including over-samples of African-American and elderly subjects). Two specific aims are advanced to test the hypotheses: (1) examine the relationship between body mass index and functional disability among men and women over the duration of the panel studies and (2) model the relationship between body mass index and assessed health over time controlling for morbidity and functional disability. The statistical analyses account for attrition due to mortality by applying selection bias models.